1. Field of the Invention
The present invention relates to a matching circuit system, and particularly to a matching circuit system that can utilize combinations of a plurality of inductors and a plurality of capacitors to suppress a second harmonic and a third harmonic of an input signal of an input stage circuit and match an input impedance of the input stage circuit.
2. Description of the Prior Art
Please refer to FIG. 1. FIG. 1 is a diagram illustrating a matching circuit 100 according to the prior art. The matching circuit 100 includes a first inductor 102, a first capacitor 104, a second capacitor 106, and a second inductor 108. The first inductor 102 and the first capacitor 104 are used for matching an input impedance GammaL of an input stage circuit 116 (such as a power amplifier or an amplifier), and forming a low-pass filter to filter a high frequency component of an input signal IS of the input stage circuit 116. The second capacitor 106 is used for blocking a direct current component of the input signal IS of the input stage circuit 116.
Although power of the input signal IS can be transmitted to an output stage circuit 118 (such as an antenna, a switch, or a next stage circuit) having a 50Ω impedance through the matching circuit 100, the matching circuit 100 cannot significantly suppress a second harmonic and a third harmonic of the input signal IS, resulting in a signal received by the output stage circuit 118 having serious harmonic distortion. Therefore, in the prior art, the signal received by the output stage circuit 118 may not match a communication specification of the Federal Communications Commission (FCC).